1. Field of the Invention
The present invention relates to a dynamo-electric machine which includes an equalizer which electrically connects commutator segments which have substantially the same electric potential, and to a method of manufacture therefor.
2. Description of the Related Art
FIG. 22 is a partial cross-section of a direct-current machine which is the dynamo-electric machine described in Japanese Utility Model Laid-Open No. (SHO) 56-149565. The direct-current machine comprises: an armature 3 secured to a shaft, having a winding 2 composed of a wire or wires wound by a lap winding method through slots formed so as to extend in the axial direction on the outer circumferential surface of a core 1; a commutator 5 secured to the shaft, comprising commutator segments 4 and risers 8; an equalizer 6 in contact with the outer surface of the commutator 5, which electrically connects commutator segments 4 which should have the same electric potential; brushes 7 in contact with the surface of the commutator segments 4; and a winding support portion 9 which supports the winding 2.
The equalizer 6 comprises: a support ring 11 having an annular groove formed on its inner wall; and equalizer coils 10 built into the annular groove stacked in layers in the axial direction. The surfaces of the equalizer coils 10 are insulated, and protruding portions 12 are formed at four locations equidistantly around the circumference of the inner circumferential surfaces thereof, as shown in FIG. 23. The protruding portions 12 are pressed into contact with the surface of the commutator segments 4 to connect commutator segments which should have the same electric potential.
One problem with the conventional direct-current machine is that the equalizer 6 is disposed radially outwards from the commutator 5, making the centrifugal force acting on the equalizer 6 that much greater, and there is a risk that the equalizer 6 may be damaged by that force.
Another problem is that the equalizer 6 is in contact with the surface of the commutator 5 and the commutator 5 must be made that much longer in the axial direction, increasing the size, and inevitably the cost, of the commutator 5.
Another problem is that the equalizer 6 and brushes 7 are close to each other and the brushes 7 hinder the installation and removal of the equalizer 6, making it difficult to work on.
Another problem is that the brushes 7 get in the way of disassembly and assembly of the direct-current machine itself, during maintenance, etc., also making it difficult to work on.